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Your search keyword '"Limberger, H.G."' showing total 113 results
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113 results on '"Limberger, H.G."'

2. Sub-quadratic dependence of visible upconversion on infra-red direct luminescence decay owing to static energy-transfer upconversion

Author

Pollnau, Markus, Fedosseev, R.V., and Limberger, H.G.

Subjects
IR-72289, IOMS-APD: Active Photonic Devices, EWI-18052
Abstract

Because of their broadband luminescence, TM-ion-doped materials are of high interest for applications as tunable and short-pulse lasers. Systems with a d1 electron configuration possess only one excited 3d level and excited-state absorption into higher-lying 3d levels is impossible. One of these d1 systems, Ti:sapphire has become the most successful tunable and short-pulse laser system to date. Mn6+ is a promising d1 ion for a tunable laser system. In BaSO4, near-infrared emission from Mn6+ was observed. The room-temperature stimulated-emission cross section is larger than the excited-state-absorption cross section in the spectral range 920-1600 nm [1], i.e., as a laser material BaSO4:Mn6+ can offer a broad tuning range. Here we report on the first epitaxial growth of Mn6+-doped BaSO4 layers. Growth techniques such as the melt growth fail, because barium sulphate has a phase transition at 1090°C and exhibits thermal decomposition at 1590°C. Therefore, we grew BaSO4 substrate crystals by the flux method. The Mn6+ ions tend to reduce to Mn5+ at T  620°C. We used a CsCl-KCl-NaCl solvent [2] for the LPE of BaSO4:Mn6+. This solvent has a low solidification temperature of 480°C and the growth process could be performed at temperatures well below 620°C. The nominal Mn6+ concentration was up to 0.8 mol%. High quality, lack of large-size inclusions, and low defect concentration were achieved. These Mn6+-doped BaSO4 layers were investigated spectroscopically by absorption, emission, and luminescence-excitation measurements at room temperature. Excitation at 800 nm leads to broadband Mn6+ emission between 850 and 1600 nm. Currently, we investigate the lasing potential of our BaSO4:Mn6+ layers. [1] T.C. Brunold, H.U. Güdel, S. Kück, G. Huber, JOSA B 14, 2373 (1997). [2] D. Ehrentraut, M. Pollnau, J. Cryst. Growth 234, 533 (2002).

Published
2002

41. Continuous-wave highly efficient phosphosilicate fibre-based Raman laser (λ = 1.24 μm)

Author

Dianov, E.M., Bufetov, I.A., Bubnov, M.M., Grekov, M.V., Shubin, A.V., Vasil'ev, S.A., Medvedkov, O.I., Semenov, S.L., Egorova, O.N., Gur'yanov, A.N., Khopin, V.F., Yashkov, M.V., Varelas, D., Iocco, A., Costantini, D.M., Limberger, H.G., and Salathe, R.P.

Abstract

An efficient fibre-based Raman laser was developed on the basis of a phosphosilicate optical fibre with low optical losses. Bragg fibre gratings, constituting the laser cavity, were formed directly in the active fibre. The parameters, mathematical modelling, and optimisation of the laser were investigated. As a result of the optimisation, the output power reached 2.4 W for pumping with radiation from a neodymium fibre-based laser with a power of 3.5 W, which corresponds to a 77% quantum efficiency of the Raman laser.

Published
1999

42. Properties of the cladding modes of an optical fibre excited by refractive-index gratings

Author

Vasil'ev, S.A., Dianov, E.M., Medvedkov, O.I., Protopopov, V.N., Costantini, D.M., Iocco, A., Limberger, H.G., and Salathe, R.P.

Abstract

The properties of the cladding modes of an optical fibre, excited by photoinduced long-period fibre gratings, were investigated by the near- and far-field methods. It is shown that the cladding modes considered are of the HE1m type. A satisfactory agreement between the experimental and calculated distributions of the electromagnetic field of the modes is demonstrated. It was found that the propagation length of a cladding mode in the unperturbed fibre reaches 1 m.

Published
1999

43. Hydrogen-induced reduction of axial stress in optical fiber cores.

Author

Nguyen Hong Ky, Limberger, H.G., Salathe, R.P., Cochet, F., and Dong, L.

Subjects
*AXIAL loads, *OPTICAL fibers
Abstract

Studies hydrogen-induced reduction of axial stress in optical fiber cores. Reduction of axial stress in the core of fibers after hydrogen loading; Radial distribution of axial stress; Summary of stress measurements obtained for all fibers.

Published
1999
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44. Compaction- and photoelastic-induced index changes in fiber Bragg gratings.

Author

Limberger, H.G. and Fonjallaz, P.-Y.

Subjects
*PHOTOELASTICITY, *REFRACTIVE index
Abstract

Examines the compaction- and photoelastic-induced index changes in fiber Bragg gratings. Significance of the photoelastic effect on refractive index; Description on the total Bragg grating index modulation; Evaluation of the form axial stress measurements, index modulation amplitude and index change of the Bragg gratings.

Published
1996
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